Prostate cancer is at the present time the most common form of cancer among men. The prostate is a walnut sized gland in men that produces fluid that is a component in semen. The prostate has two, or more, lobes, or sections, enclosed by an outer layer of tissue. The prostate is located in front of rectum and just below the urine bladder, and surrounds the urethra.
The occurrence of prostate cancer is highest in the northwestern part of Europe and in the United States. The growth of the tumour is usually a procedure that takes place during a long period of time. Prostate cancer is normally a mild form of cancer. In fact, the majority of men diagnosed with prostate cancer do survive, and only a minority of the men encounter a more aggressive form of prostate cancer, which metastasizes in an early stage. This form of prostate cancer may only be curable if it is diagnosed in an early stage, before the cancer has spread to extracapsular tissue.
The most common prostate problem is not prostate cancer, but prostate inflammation Or infection, called prostatitis, and prostate enlargement (benign prostatic hyperplasia or BPH).
It is very common that different prostate problems have similar symptoms, such as frequent and urgent need to urinate, beginning a stream of urine. It is also a fact that a man in the early stages of prostate cancer may have no symptoms at all. This confusing array of symptoms makes a thorough medical examination and testing very important.
Today diagnosis and monitoring of prostate cancer may be performed by measuring the concentration of a prostate specific antigen (PSA) in the blood of the patient. If the concentration of PSA is markedly high in several consecutive measurements, performed at different points of time, the assessment is that there is a probability of prostate cancer. At this point of time a biopsy may be performed to verify prostate cancer.
PSA is a protein, constituted of a single chain of 237 amino acids, that is produced in the secretory cells of the prostate. These secretory cells may be found in the whole prostate gland. PSA is well established and thoroughly researched marker in respect of prostate cancer. By comparison with healthy cells the production of PSA is lower in malign cells and higher in hyperplastic cells. It is therefore contradicting that in fact the concentration of PSA is higher in blood from men suffering from prostate cancer. However, one explanation may be that the malign cells have a deteriorated cell structure, and are therefore more permeable to PSA.
Men suffering from benign prostatic hyperplasia (BPH) do also have an increased concentration of PSA in the blood. The increased concentration of PSA, in the blood of men with BPH, is directly proportional to the volume increase of the prostate gland. Also men suffering from prostatitis and gland trauma have an increased concentration of PSA in the blood.
This presents a problem in the diagnosis and monitoring of the different prostate complications. It may be impossible to distinguish between the different complications without performing biopsies of the prostate gland. A biopsy is a surgical procedure, which cause pain and discomfort. Patients awaiting a biopsy may suffer from anxiety prior to the surgical procedure, and it is common that the patient therefore has to take some kind of anxiolytic before the surgical procedure. Other problems with biopsy are that the tumour is missed, which may result in an erroneous diagnosis; risk of infection; the concentration of PSA increases after biopsy, since the cell structure is damaged and the permeation of PSA therefore increases; and formation of scars, which results in an altered structure of the prostate tissue that render future biopsy procedures difficult. Further problems with biopsy are transient haematuria (blood in the urine) and the use of blood-thinning agents.
Another important serine protease, which may be suitable for future diagnosis of prostate malfunction, is human glandular kallikrein 2 (hK2). The gene coding hK2 is located on chromosome 19, together with the gene coding for PSA. hK2 is expressed mainly in the prostate tissue, just as PSA. Immunohistochemical research in respect of hK2 has shown that hK2 is expressed in relation to the level of differentiation. This means that hK2 is expressed in a higher yield in tissue of low differentiation, such as tissue subjected to prostate cancer, and in a lower yield in tissue of high differentiation, such as tissue subjected to BPH.
Positron Emission Tomography (PET) is today used as a radio diagnostic method to detect and evaluate neoplasia. PET utilises the increased level of glycosylation in malign tissue. Radiolabelled glucose analogues are injected intravenously. Thereafter, the gamma radiation is detected to determine the consumption of glucose. Areas comprising cells with a high consumption of glucose are visualised as areas of high attenuation. A three dimensional picture may be created by adding picture screens, which have been produced by the tomography. This technique may be combined with computer tomography (CT) or magnetic resonance tomography (MRT), to obtain the exact anatomic location of the attenuated structure.
Thus, there is a need for a new diagnostic method for establishing and distinguishing prostate cancer from other prostate complications, such as prostatitis, and benign prostatic hyperplasia.
Hence, an improved diagnostic method for establishing and distinguishing prostate cancer would be advantageous and in particular a diagnostic method allowing for differentiation between prostate cancer and other prostate complications, such as benign prostatic hyperplasia, and prostatitis, which diagnostic method also may be used to investigate metastasis, such as lymph gland metastasis, post operative examinations, and examinations during or after radiation, cytostatic, and androgen treatments, would be advantageous, said method also avoiding the above deficiencies in respect of biopsy.